Prior studies suggest that women with intellectual and developmental disabilities and their infants are at elevated risk of having adverse obstetric health outcomes. Yet, there is no research on pregnancy or infant health outcomes with a population-based sample of US women with intellectual and developmental disabilities or their infants. As a result, many questions remain unanswered about the unmet perinatal health care needs and health outcomes of women with intellectual and developmental disabilities. In the proposed study, we plan to address this gap in the literature and use our findings to develop perinatal care recommendations to improve care for women with intellectual and developmental disabilities. The specific aims of this study are to (1) Investigate pregnancy and childbirth complications, outcomes, and inpatient costs among women with intellectual and developmental disabilities and women in the general US obstetric population, (2) Examine longitudinal health outcomes and health care utilization and costs of women with intellectual and developmental disabilities around the time of their pregnancy and for their infants (up to 1 year of age) compared to other women, and (3) Identify unmet needs and barriers to perinatal care for women with intellectual and developmental disabilities through in-person interviews with pregnant women and new mothers with IDD and telephone interviews with the health care professionals who provide their health care. The study will be conducted using nationally-representative population-based data from the Healthcare Cost and Utilization Project (HCUP) and the Massachusetts Pregnancy to Early Life Longitudinal-All Payer Claims Database (PELL-APCD) linked data system to determine differences in perinatal health care utilization, outcomes, and costs between women with and without intellectual and developmental disabilities and their infants. Finally, the study will develop perinatal care recommendations, providing clinicians with practical tools to address the unique needs of this highly vulnerable population of women with IDD.